The study on the bedrock groundwater flow is limited in Japan because of its less yield capacity as a groundwater resources. However, recently the study for these bedrock groundwater has become important because of the construction of the deep underground civil structure. It cab be thought that the relatively high driving force of the bedrock gorundwater be exist in the mountanious and humid country as Japan.Alluvial fan which exists between mountain range and flat plain is a turning point of the ground surface inclination. These place must have the strong upward groundwater flow in the bedrock. Depend on this idea, the present study has selected the Imaichi alluvial fan, Tochigi prefecture of Japan to study the groundwater flow both in the alluvial gravel aquifer and in the bedrock fracture aquifer and also to make clear the interrelation between them within the framework of the regional ground water flow.The used methods are the conventional groundwater investigation for the gravel aquifer, river water discharge analysis, paleo-hydrological investigation for the gravel aquifer, three dimensional steady state groundwater simulation of the regional scale, two boreholes with 200 m depths to leach bedrock aquifer penetrate gravel zone, groundwater potential measurement by using these boreholes, groundwater sampling from different depth of the bedrock aquifer by using boreholes and water chemistry analysis and environmental isotope analyzes (tritium, C-14, He-3, D and 0-18), groundwater temperature profile measurement. The investigation has been done for more than two years on the different seasons. The results of these measurements makes clear the regional groundwater flow of the study area including bedrock groundwater.